1. Field of the Invention
The invention relates to a vehicle control apparatus and method that executes a neutral control that forcibly places an automatic transmission of a vehicle in a substantially neutral state when the shift position of the automatic transmission is in the drive position and a catalyst heating control that increases the temperature of a catalyst provided in the exhaust system.
2. Description of the Related Art
An exhaust gas purification device for internal combustion engines, such as vehicle diesel engines, reduces the particulate matter (PM: Particulate Matter) discharged outside of the internal combustion engine by trapping the particulate matter contained in the exhaust gas discharged from the internal combustion engine using an exhaust gas purification catalyst provided in an exhaust passage. Normally, the function of such an exhaust gas purification catalyst deteriorates as the amount of the particulate matter accumulated in the exhaust gas purification catalyst increases. Therefore, in response to the amount of the accumulated particulate matter exceeding a reference amount, a catalyst heating control is executed to increase the temperature of the exhaust gas purification catalyst so that the accumulated particulate matter is combusted and thus removed.
Meanwhile, in vehicles having an automatic transmission, even when the shift position of the automatic transmission is in the drive position, a so-called neutral control, which is a control for forcibly placing the automatic transmission in a substantially neutral state, is executed in order to improve the fuel economy if predetermined conditions, such as the accelerator operation amount being equal to or smaller than a predetermined amount, are satisfied. However, because the load of the internal combustion engine decreases during the neutral control, if the duration of the neutral control is excessively long, it leads to a decrease in the exhaust gas temperature. As such, in vehicles in which the neutral control and the aforementioned catalyst heating control are both executed, if the neutral control is executed during the catalyst heating control, it may cause a decrease in the exhaust gas temperature and thus may make it difficult for the accumulated particulate matter to be combusted and thus removed, resulting in a delay in recovering the function of the exhaust gas purification catalyst.
In view of this, in the vehicle recited in Japanese Patent Application Publication No. JP-2004-44722 (JP-A-2004-44722), the execution of the neutral control is restricted during the catalyst heating control. As such, the foregoing decrease in the exhaust gas temperature is suppressed, whereby the temperature of the exhaust purification catalyst is reliably increased. Therefore, the accumulated particulate matter is efficiently combusted and thus removed, so that the function of the exhaust gas purification catalyst is recovered reliably.
However, in the vehicle recited in Japanese Patent Application Publication No. JP-2004-44722, the reduction of the fuel economy resulting from the restriction on the neutral control is not ignorable although it is true that such restriction on the neutral control helps recover the function of the exhaust gas purification catalyst reliably as mentioned above. Further, executing the neutral control unavoidably causes a delay in recovering the function of the exhaust gas purification catalyst although contributing to improving the fuel economy.
Such problems occur not only to vehicle control apparatuses adapted to execute a control for increasing the temperature of a catalyst to combust and thus remove particulate matter in the catalyst, but also to vehicle control apparatuses that execute a catalyst heating control for various other purposes, such as those adapted to execute a control for increasing the temperature of a catalyst to remove sulfur in the catalyst.